Graphical views provide user-friendly ways to analyze how data varies with respect to one or more parameters. In some graphical views, variation of data with respect to one or more parameters is illustrated by varying one or more visual properties of marks that correspond to respective data points. For example, marks that cover respective specified areas in a graphical view, which are referred to as area marks, may have colors or patterns that vary based on values of corresponding data. In another example, point marks displayed at distinct locations in a graphical view may have sizes that vary based on values of corresponding data. Sometimes a “graphical view” is referred to as a “data visualization.”
Map views provide an intuitive way to examine geographical variation of data. Two common examples of map views are choropleth maps, which are also referred to as filled maps, and proportional symbol maps. For choropleth maps, the marks are colors or patterns used to fill respective geographical regions; these marks are examples of area marks. For proportional symbol maps, symbols displayed at respective geographical locations vary by size in proportion to values of a parameter at the respective geographical locations or corresponding regions. These symbols are examples of point marks. A map view is one data visualization type. Other data visualization types include charts, such as bar charts.
There is a need for user-friendly software to generate graphical views of data, such as map views. In particular, a user may desire to associate data with one or more visual mark properties and in response have appropriate symbols be displayed automatically. The user also may desire to modify the association of data with visual mark properties and have the graphical view update automatically.